Coen brothers easily for their bout.
NOlan and Stone are close, because I think at his peak Stone did some of the most viceral and stunning films in the '80s and '90s including Platoon, Born on the Fourth of July, JFK and Wall Street.
But then he went off the deep end and made two of the worst movies I have ever with U-Turn and the only movie I ever walked out in (mind you it was on DVD) with Natural Born Killers (and I've watched some pretty crappy movies in my day). Alexander was a huge disappointment as well.
Nolan hasn't done a bad movie and while Memento is the only amazing movie he has done thus far, he proves he has a lot up his sleeve and is growing and I see a career with potential longevity that has far from peaked. In fact The prestige felt more like his "Pledge" that the best is yet to come.
With that said how the **** did Nolan beat Robert Altman, now? Again, WTF, mate? Nolan himself would vote for Altman between the two, really.